test: rename 'test-push-r.t' to 'test-push.t'
We do not have a simple test for 'hg push' but we have multiple tiny tests for
various aspect of it. We'll unify them into a single file, and we start with
'test-push-r.t'. The code is unchanged but we renamed the repository used to
avoid collision with other tests we'll import in coming changesets.
Test timing for the record:
start end cuser csys real Test
1.850 2.640 0.650 0.090 0.790 test-push-validation.t
2.640 3.520 0.760 0.090 0.880 test-push-hook-lock.t
0.000 1.850 1.560 0.210 1.850 test-push-r.t